Dear John
>I have an app which needs to send ASCII g-codes to a numerically controlled
>machine. I can generate the g-codes, but have no idea at all how to send
>them (wouldn't even know where to start).
>Is anyone able to give me the run-down.

I don't know what is g-code. 
I assume you can generate the g-codes.
and you have a proper cable to NC machie.

Below is what you need!?

' ###########################################
GLOBALS 
DIM gEnds
END GLOBALS

'funcitons
LOCAL FN openJohnDevice(port%)
  'OPEN "C",portID [,baud] [,parity] [,stopbit] [,wordLen] [,buffer]
  OPEN "C", port%,19200,_evenParity,_oneStopBit,_eightBits                
                                                        
'
' you must update what kind of handshake
 HANDSHAKE port%,_none                           '_cts
END FN

LOCAL FN sendCmdJohnDevice(s$)                  
  PRINT # gSerialPort, s$; 
END FN

'main
port%=_modemport
FN openJohnDevice(port%)

DO 
 HANDLEEVENTS
' Build command by yourself
 FN sendCmdJohnDevice(s$)
UNTIL gEnds

' *************************************
Good Luck!

Masakazu Nakao
masa.nakao@...